Test Circuit and Method for Reverse Recovery Unit (RPU) Protection Setting of Thyristor Valve

Abstract

This invention discloses a test circuit and method for the protection setting of a thyristor valve reverse recovery protection unit (RPU). The test circuit includes a primary circuit and a secondary trigger circuit. An impulse voltage is output to the RPU board through an impulse voltage source. The RPU outputs a protection trigger pulse to turn on the optically triggered thyristor. This test circuit and test method can be equivalent to actual working conditions and accurately measure the protection setting of the RPU.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a test circuit and method for the protection setting value of a thyristor valve reverse recovery protection unit (RPU). Background Technology

[0002] Optically triggered thyristor converter valves (hereinafter referred to as "optically controlled valves") are widely used in DC engineering. Unlike electrically controlled thyristor converter valves (hereinafter referred to as "electrically controlled valves"), which place monitoring, triggering and protection on the same board, optically controlled valves use different boards to achieve the above-mentioned different functions. Among them, the RPU board is specifically used to realize the thyristor reverse recovery period protection function.

[0003] The specific function of the RPU board is to detect the rate of change of voltage (dV / dt) across the thyristor stage after receiving the reverse recovery period protection enable signal from the valve control device. When the detected value exceeds the protection setpoint, a laser trigger pulse is emitted, which is then sent to the thyristor gate after being split by the MSC to trigger its conduction. To ensure that the RPU board can reliably recognize the enable signal and output the trigger pulse to trigger the thyristor conduction at the correct dV / dt, single-board testing is required after the board is manufactured. Since it is inconvenient to install the RPU into the valve module for testing, the equivalent testing method is currently used.

[0004] Patents CN206892216U and CN105510730B propose an equivalent testing device and method for an RPU board. Both methods involve applying an external impulse voltage to excite the RPU board, causing it to output a trigger pulse when the enable signal is valid. The detection of this trigger pulse determines whether the RPU board's protection function is normal. While this device and method can perform single-board testing outside the actual working environment of the RPU board, it only detects whether the RPU board emits a trigger pulse and does not verify whether the thyristor is ultimately triggered to conduct.

[0005] CN107765118B adds the detection of the trigger pulse width of the RPU board based on the above two patents. However, in reality, the trigger pulse required to turn on the optical trigger thyristor needs to have a certain amplitude in addition to the width. Moreover, the width and amplitude are not two unrelated constant values, but rather they meet certain conditions. Therefore, it is impossible to give a unique criterion for the critical trigger pulse waveform. That is, it is inaccurate and unrigorous to measure the protection function by detecting the trigger pulse output by the RPU board.

[0006] Therefore, it is necessary to design a test circuit and test method that directly uses whether the thyristor can be triggered to conduct as the test criterion for whether the protection function of the RPU board is qualified. This can accurately measure the dV / dt protection setting of the RPU board, ensuring that its function meets the design requirements and satisfies the engineering operation. Summary of the Invention

[0007] The purpose of this invention is to propose a test circuit and method for the protection setting value of the thyristor valve reverse recovery protection unit (RPU), in order to solve the problem that in the prior art, when testing the RPU board, only testing its output protection trigger pulse cannot truly reflect whether the RPU can reliably trigger the optical thyristor to conduct.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] As a first aspect of the present invention, a test circuit for the protection setting value of the reverse recovery protection unit (RPU) of a thyristor valve is provided, the test circuit comprising a primary main circuit and a secondary trigger circuit;

[0010] The primary main circuit includes a DC power supply, a current-limiting resistor, an optically triggered thyristor, and an air switch connected in series.

[0011] The secondary triggering circuit includes an impulse voltage source, a voltage limiting resistor, a voltage dividing capacitor, a beam splitter, and an optical trigger thyristor valve reverse recovery protection unit (RPU). The impulse voltage source and the voltage limiting resistor are connected in parallel. One end of the voltage dividing capacitor is connected to the common terminal of the high-voltage side of the impulse voltage source, and the other end is connected to one electrical input terminal of the optical trigger thyristor valve reverse recovery unit (RPU). The other electrical input terminal of the optical trigger thyristor valve reverse recovery unit (RPU) is connected to the common terminal of the low-voltage side of the impulse voltage source. The optical emission port of the optical trigger thyristor valve reverse recovery protection unit (RPU) is connected to the optical receiving port of the beam splitter via a trigger optical fiber, and the optical emission port of the beam splitter is connected to the gate of the optical trigger thyristor via a trigger optical fiber.

[0012] Preferably, the beam splitter is a multi-star coupled beam splitter.

[0013] Preferably, the positive voltage direction of the DC power supply is consistent with the current flow direction of the optically triggered thyristor.

[0014] Preferably, the DC power supply has an adjustable voltage and includes voltage and current display functions.

[0015] Preferably, the test circuit further includes an oscilloscope for observing the actual output voltage waveform of the impulse voltage source.

[0016] Preferably, the voltage amplitude and pulse width of the impulse voltage source are adjustable.

[0017] As another aspect of this application, a test method for the above-mentioned test circuit is proposed, including:

[0018] Step 1: Close the air switch in the primary circuit and adjust the output voltage of the DC power supply from 0 to an amplitude that allows the optical trigger thyristor to be reliably triggered and turned on. Monitor the voltage and current output by the DC power supply to ensure that the optical trigger thyristor is in the blocking state at this time.

[0019] Step 2: Set the voltage rise rate of the impulse voltage source to D1, where D1 is the initial set value of the voltage rise rate;

[0020] Step 3: After the impulse voltage source outputs the impulse voltage, monitor the current amplitude of the DC power supply to determine whether the optical trigger thyristor is turned on. If it is not turned on, reset the impulse voltage source to increase the actual output voltage rise rate by Δd. If it is turned on, reset the impulse voltage source to decrease the actual output voltage rise rate by Δd, where Δd is the setting step size.

[0021] Step 4: Repeat step 3 until the critical voltage rise rate D2 is found, so that the optically triggered thyristor can be reliably turned on.

[0022] Step 5: Calculate the protection setting value of the optically triggered thyristor valve reverse recovery protection unit (RPU) based on the critical voltage rise rate D2: D2 * C k / C g C k C is the capacitance value of the valve section equalizing capacitor connected in series with the reverse recovery protection unit (RPU) of the converter valve and the light-triggered thyristor valve. g This is to test the capacitance value of the voltage divider capacitor in the circuit.

[0023] Preferably, the DC power supply is considered to be conducting when the current amplitude is greater than a preset current threshold; otherwise, it is considered not conducting.

[0024] The beneficial effect of this invention is that by adding a circuit consisting of an optically triggered thyristor and other primary devices to the test circuit, the conduction of the thyristor is directly used as the criterion for whether the RPU protection is effective. This solves the shortcomings of the previous method of judging only the trigger pulse, which was not rigorous and inaccurate. It can test the dV / dt protection setting of the RPU very accurately. Attached Figure Description

[0025] In the accompanying drawings (which are not necessarily drawn to scale), similar reference numerals may describe similar parts in different views. Similar reference numerals with different letter suffixes may indicate different examples of similar parts. The drawings illustrate, by way of example and not limitation, the various embodiments discussed herein.

[0026] Figure 1 This invention provides a test circuit for the protection setting of a thyristor valve reverse recovery protection unit (RPU).

[0027] Figure 2 The testing method described in the application scenario of this invention embodiment. Detailed Implementation

[0028] The invention will now be described in detail with reference to a specific example.

[0029] like Figure 1 The circuit shown is the test circuit for the protection setting of the thyristor valve reverse recovery protection unit (RPU) in this embodiment, which includes a primary main circuit and a secondary trigger circuit.

[0030] The primary circuit is the conduction circuit of the optically triggered thyristor, including a DC power supply, a current-limiting resistor, the optically triggered thyristor, and an air switch. These components are connected in series via wires to form a single loop. In this embodiment, the current-limiting resistor is 20Ω. The positive voltage direction of the DC power supply is consistent with the current flow direction of the optically triggered thyristor. The DC power supply voltage can be adjustable from 0 to 1kV. In some embodiments, the DC power supply voltage has real-time voltage and current display functions. The purpose of setting up the primary circuit is to convert the RPU's protection signal into the thyristor's conduction state, thereby directly and reliably testing the effectiveness and reliability of the RPU protection.

[0031] The secondary trigger circuit is the drive circuit for the optically triggered thyristor, including an impulse voltage source, a voltage limiting resistor Rs, a voltage dividing capacitor Cg, a beam splitter, and an optically triggered thyristor valve reverse recovery protection unit (RPU). The function of the secondary circuit is to apply the impulse voltage to the RPU and generate a protection signal by adjusting the voltage rise rate.

[0032] In this embodiment, the selected impulse voltage source has an adjustable output voltage amplitude of 0–10kV and an adjustable pulse width of 1–5µs. The impulse voltage source and the voltage limiting resistor Rs are connected in parallel to form a whole. One end of the voltage divider capacitor Cg is connected to the common terminal of the high-voltage side of the impulse voltage source, and the other end is connected to one electrical input terminal X1 of the optically triggered thyristor valve reverse recovery unit RPU. The other electrical input terminal X2 of the optically triggered thyristor valve reverse recovery unit RPU is connected to the common terminal of the low-voltage side of the impulse voltage source.

[0033] One optical transmitter port of the optically triggered thyristor valve reverse recovery protection unit (RPU) is connected to one optical input port of the beam splitter via a trigger fiber. One optical output port of the beam splitter is connected to the gate of the optically triggered thyristor via a trigger fiber. The beam splitter is used to distribute a higher-power laser trigger signal into a lower-power optical trigger signal, which serves as the gate drive signal for triggering the optically triggered thyristor to conduct.

[0034] In preferred embodiments, the beam splitter is often a multi-star coupled beam splitter (MSC).

[0035] In a preferred embodiment, the test circuit further includes an oscilloscope for observing the actual output voltage waveform of the impulse voltage source.

[0036] A test method for a thyristor valve reverse recovery protection unit (RPU) protection setting test circuit based on the above test circuit is as follows: Power on the test circuit and operate according to the following steps:

[0037] Step 1: Close the air switch in the primary circuit and adjust the output voltage of the DC power supply to an amplitude that enables the optical trigger thyristor to be reliably triggered and turned on. In this embodiment, it is 120V. Monitor the voltage and current output of the DC power supply to ensure that the optical trigger thyristor is in the blocking state at this time.

[0038] Step 2: Set the voltage rise rate of the impulse voltage source to D1, where D1 is the initial value of the voltage rise rate. In this embodiment, the voltage rise rate D1 is selected as 1kV / us, which is obtained by measuring the actual output voltage waveform of the impulse voltage source with an oscilloscope.

[0039] Step 3: After the impulse voltage source outputs the impulse voltage, monitor the current amplitude of the DC power supply to determine whether the optically triggered thyristor is conducting. If it is not conducting, reset the impulse voltage source to increase the actual output voltage rise rate by Δd. If it is conducting, reset the impulse voltage source to decrease the actual output voltage rise rate by Δd, where Δd is the setting step size. In this embodiment, the step size is set to 0.1kV / us. When the current voltage rise rate is 1kV / us, if the optically triggered thyristor is not conducting, reset the impulse voltage source to increase the actual output voltage rise rate to 1kV / us + 0.1kV / us. If it is conducting, reset the impulse voltage source to increase the actual output voltage rise rate to 1kV / us - 0.1kV / us. The specific method for determining whether the optically triggered thyristor is conducting is as follows: when the current amplitude of the DC power supply is greater than a preset current threshold, it is considered conducting; otherwise, it is considered not conducting.

[0040] Step 4: Repeat step 3 until a critical voltage rise rate D2 is found that allows the optically triggered thyristor to reliably conduct.

[0041] Step 5: Query the capacitance value of the valve section equalizing capacitor connected in series with the reverse recovery protection unit (RPU) of the actual converter valve and light-triggered thyristor valve, which is C. k The capacitance of the voltage divider capacitor in the test circuit is C. g The protection setting of the reverse recovery protection unit (RPU) for the optically triggered thyristor valve is calculated based on the critical voltage rise rate D2: D*C. k / C g .

[0042] The innovation of the test circuit and test method described in this embodiment lies in the addition of a circuit composed of an optically triggered thyristor and other primary devices to the test circuit. The conduction of the thyristor is directly used as the criterion for whether the RPU protection is effective. This solves the shortcomings of the previous method, which only judged the trigger pulse and was not rigorous and accurate. It can test the dV / dt protection setting of the RPU very accurately.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A test circuit for the protection setting value of a thyristor valve reverse recovery protection unit (RPU), characterized in that, The test circuit includes a primary main circuit and a secondary trigger circuit; The primary main circuit includes a DC power supply, a current-limiting resistor, an optically triggered thyristor, and an air switch connected in series. The secondary triggering circuit includes an impulse voltage source, a voltage limiting resistor, a voltage dividing capacitor, a beam splitter, and an optical trigger thyristor valve reverse recovery protection unit (RPU). The impulse voltage source and the voltage limiting resistor are connected in parallel. One end of the voltage dividing capacitor is connected to the common terminal of the high-voltage side of the impulse voltage source, and the other end is connected to one electrical input terminal of the optical trigger thyristor valve reverse recovery unit (RPU). The other electrical input terminal of the optical trigger thyristor valve reverse recovery unit (RPU) is connected to the common terminal of the low-voltage side of the impulse voltage source. The optical emission port of the optical trigger thyristor valve reverse recovery protection unit (RPU) is connected to the optical receiving port of the beam splitter via a trigger optical fiber, and the optical emission port of the beam splitter is connected to the gate of the optical trigger thyristor via a trigger optical fiber.

2. The test circuit as described in claim 1, characterized in that, The beam splitter is a multi-star coupled beam splitter.

3. The test circuit as described in claim 1, characterized in that, The positive voltage direction of the DC power supply is consistent with the current flow direction of the optically triggered thyristor.

4. The test circuit as described in claim 1, characterized in that, The DC power supply has an adjustable voltage and features voltage and current display functions.

5. The test circuit as described in claim 1, characterized in that, The test circuit also includes an oscilloscope for observing the actual output voltage waveform of the impulse voltage source.

6. The test circuit as described in claim 1, characterized in that, The voltage amplitude and pulse width of the impulse voltage source are adjustable.

7. The test method for the test circuit as described in any one of claims 1 to 6, characterized in that, include: Step 1: Close the air switch in the primary circuit and adjust the output voltage of the DC power supply from 0 to an amplitude that allows the optical trigger thyristor to be reliably triggered and turned on. Monitor the voltage and current output by the DC power supply to ensure that the optical trigger thyristor is in the blocking state at this time. Step 2: Set the voltage rise rate of the impulse voltage source to D1, where D1 is the initial set value of the voltage rise rate; Step 3: After the impulse voltage source outputs the impulse voltage, monitor the current amplitude of the DC power supply to determine whether the optical trigger thyristor is turned on. If it is not turned on, reset the impulse voltage source to increase the actual output voltage rise rate by Δd. If it is turned on, reset the impulse voltage source to decrease the actual output voltage rise rate by Δd, where Δd is the setting step size. Step 4: Repeat step 3 until the critical voltage rise rate D2 is found, so that the optically triggered thyristor can be reliably turned on. Step 5: Calculate the protection setting value of the optically triggered thyristor valve reverse recovery protection unit (RPU) based on the critical voltage rise rate D2: D2 * C k / C g C k C is the capacitance value of the valve section equalizing capacitor connected in series with the reverse recovery protection unit (RPU) of the converter valve and the light-triggered thyristor valve. g This is the capacitance value of the voltage divider capacitor in the test circuit.

8. The test method for the test circuit as described in claim 7, characterized in that, The DC power supply is considered to be conducting when the current amplitude is greater than the preset current threshold; otherwise, it is considered not conducting.

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